//返回角度  
function GetSlideAngle(dx, dy) {
  return Math.atan2(dy, dx) * 180 / Math.PI
}
//根据起点和终点返回方向 1：向上，2：向下，3：向左，4：向右,0：未滑动  
function GetSlideDirection(startX, startY, endX, endY) {
  const dy = startY - endY
  const dx = endX - startX
  let result = 0 
  //如果滑动距离太短
  if (Math.abs(dx) < 2 && Math.abs(dy) < 2) {
    return result
  }
  const angle = GetSlideAngle(dx, dy)
  if (angle >= -45 && angle < 45) {
    result = 4
  } else if (angle >= 45 && angle < 135) {
    result = 1
  } else if (angle >= -135 && angle < -45) {
    result = 2
  } else if ((angle >= 135 && angle <= 180) || (angle >= -180 && angle < -135)) {
    result = 3
  }
  return result
}
export {
  GetSlideDirection
}
